Conventional microwave oven cooking generally involves having to periodically reposition an article being cooked and/or to adjust the oven power to lessen uneven cooking; or excessive weight loss and concomitant dryness of the article being cooked; or criticality of timing the cooking interval; or having to cook a plurality of articles (e.g.: meal components such as potatoes, vegetables, and meat) sequentially rather than simultaneously. Moreover, because frozen foods are much less effective than unfrozen foods with respect to converting microwave energy to heat, the cooking of frozen foods in microwave ovens conventionally requires either pre-cooking thawing and/or relatively elaborate control of and changes of microwave power. That is, low power or periodic power ON intervals to effect thawing, and relatively high continuous power to effect cooking.
With respect to addressing the problem of uneven cooking in microwave ovens, rotating mode stirrers have been provided to lessen non-uniformity of the field of microwave energy in microwave ovens, and rotating shelves have been introduced to lessen the effects of non-uniform fields of microwave energy in microwave ovens. U.S. Pat. No. 3,819,900 which issued June 15, 1974 to Richard Ironfield discloses such a rotating mode stirrer and U.S. Pat. No. 3,428,772 which issued Feb. 18, 1969 to K. H. Wallenfels discloses such a rotating shelf.
The prior art further discloses a number of microwave cooking containers and the like which comprise selective shielding and/or microwave transparent apertures of various sizes in structures that are otherwise microwave reflective. For instance, U.S. Pat. No. 3,547,661 which issued Dec. 15, 1970 to P. N. Stevenson discloses a container and food heating method wherein apertures of various sizes are provided in the top and bottom and are in registered relation. Such apertures may also be partially masked by microwave reflective material as indicated in FIGS. 1 and 3, areas 25 through 28. The various sizes of apertures and partial masking ostensibly provide means for selectively heating different items to different temperatures simultaneously; reference Abstract Of The Disclosure. However, this patent teaches away from the present invention by stating that areas of cross hatched lines of aluminum with intermediate spaces of equal width will pass half the radiation; reference column 3, lines 17-21 inclusive. In fact, relatively small cross hatching will substantially obviate transmission of microwave energy (consider for example, the small holes in the shield component of the door of a microwave oven), and relatively large cross hatching will be substantially ineffective with respect to blocking radiation. U.S. Pat. No. 4,013,798 which issued Mar. 22, 1977 to Costas E. Goltsos also discloses a selectively shielded microwve cooking structure comprising registered openings of various sizes.
The contemporary use of apertures of various sizes and/or shapes which are disposed in the top of a microwave cooking food tray which is otherwise microwave reflective are disclosed in U.S. Pat. No. 3,672,916 which issued June 27, 1972 to H. J. Virnig, and in U.S. Pat. No. 3,219,460, which issued Nov. 23, 1965 to E. Brown.
Prior art means for venting and/or selectively venting microwave cooking trays and packages are disclosed by Goltsos and Virnig which are referenced above, and by U.S. Pat. No. 2,633,284 which issued Mar. 31, 1953 to H. J. Moffett et al, and U.S. Pat. No. 3,188,215 which issued June 8, 1965 to W. T. Snow, Jr. Goltsos' package is vented by rupturing weakened areas with water vapor pressure; Virnig and Snow provide venting through the use of heat retractible membranes such as heat shrinkable thermoplastic; and Moffett et al provide venting through the use of meltable plugs. Also, U.S. Pat. No. 4,027,132 which issued May 31, 1977 to Melvin L. Levinson discloses selectively shielded pie baking utensils which comprise microwave reflective elements (e.g., cover 6 and plate 17) having steam/vapor passageways through them.
Prior art in the field of cooking wraps includes, for instance U.S. Pat. No. 3,042,532 which issued July 3, 1962 to G. Daline. Daline discloses a wrapper having spaced recesses filled with seasoning and which may be perforated to enable seasoning mobility and/or venting. However, it is believed that the wrap is not identified as comprising microwave reflective materials and having microwave transparent zones such as are included in the present invention.
Further, with respect to wraps, a cookbook entitled "Variable Power Microwave Cooking From Litton" (Copyrighted in 1975 by Litton Systems, Inc.) suggests on page 9 that small pieces of aluminum foil can be used to cover spots on large pieces of meat which appear to be overcooking. That is, such foil can be applied during the cooking interval to selectively shield done portions of a large piece of roast.
Additionally, while it is not believed to be prior art with respect to this invention, R. V. Decareau, Ph.D., has disclosed that perforated end caps can be used to protect the ends of otherwise unshielded, relatively long cylindrical roasts from overcooking in a microwave oven; Reference 1977 International Microwave Power Symposium Summaries, Minneapolis, Minnesota, May 24-27, 1977.
To summarize the prior art, some of the problems associated with microwave cooking have been solved in part by prior art developments. However, it is believed that the prior art has not addressed providing means such as the microwave moderators of the present invention for moderating the rate of cooking during the course of cooking, and/or moderating the microwave energy field to make it more uniform inside an enclosure containing the matter to be cooked, and has not solved the problems of microwave cooking to the same extent nor to the same degree as provided by the present invention. That is, by providing both static and dynamic microwave energy moderators, and bags, wraps, vessels, oven liners, and packages comprising such moderators which facilitate more uniform cooking with reduced attention, retaining more weight, and rendering microwave cooking less dependent on precisely timing cooking intervals.